How to drive the normal node with an empty?
I propose a similar setting, but where the normal is driven by a vector defined by the difference between the empty location and the rendered point location (that could be whole sphere location instead).
Here is opposite views when the empty is moving:

Here is the material setup:


The driver is set on the location vector of a mapping (with no input)
From that there is the calculation of the difference between the driven values and the rendered location
The output is normalized and plugged as normal vector

Each driven axis is defined this way, respectively for X, Y and Z: